1. Field of the Invention
The present invention relates to a blasting apparatus suitable for carrying out a surface treatment of sintered products such as rare earth metal-based permanent magnets and ceramics.
2. Description of the Related Art
A blasting apparatus is conventionally used for a surface treatment of, for example, rare earth metal-based permanent magnets, i.e., a treatment for removing an oxide layer formed on the surface, a treatment for cleaning the surface or a shot peening for finishing a film formed on the surface.
There are various types of blasting apparatus. For example, in a tumbler-type blasting apparatus, work pieces are placed into a drum within the apparatus, and an injection nozzle is disposed so as to inject a blast material against the work pieces through an opening in the drum, while stirring the work pieces by rotating the drum (see Japanese Patent Application Laid-open No.11-347941).
A blasting apparatus as described above is capable of mass-treatment of work pieces and excellent in productivity. In such apparatus, however, the injection of the blast material against the work pieces can be conducted only through the opening in the drum, and hence, there is, of course, a limit in respect of the treating efficiency. When an attempt is made to stir the work pieces as homogenously as possible by prolonging the treating period of time or by increasing the rotational speed of the drum in order to enhance the treating efficiency, the collision of the work pieces against one another occur frequently and with a strong shock force. For this reason, a cracking and breaking is produced in many of the work pieces. The stirring of the work pieces must be carried out, so that they are not dropped out through the opening and hence, the setting of the stirring condition is accompanied by a limitation. Further, it is necessary to place and remove the work pieces into and out of the drum before and after the treatment and hence, during the placing and removal, a cracking and breaking may be caused in the work pieces.
Accordingly, it is an object of the present invention to provide a blasting apparatus, which is excellent in treating efficiency of work pieces, and in which the occurrence of the cracking and breaking of the work pieces can be inhibited.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a blasting apparatus, comprising a tubular barrel formed of a mesh net for accommodation of work pieces and rotatable about a center axis, and an injection nozzle disposed to inject a blast material against the work pieces from the outside of the tubular barrel.
According to a second aspect and feature of the present invention, in addition to the first feature, the inside of the tubular barrel is divided into two or more accommodating sections.
According to a third aspect and feature of the present invention, in addition to the second feature, the inside of the tubular barrel is divided radiately from the center axis into two or more accommodating sections.
According to a fourth aspect and feature of the present invention, in addition to the first feature, the tubular barrel is detachably mounted.
According to a fifth aspect and feature of the present invention, there is provided a blasting apparatus, comprising a tubular barrel formed of a mesh net for accommodation of work pieces and supported circumferentially outside a center axis of a support member rotatable about the center axis, for rotation about the center axis, so that the tubular barrel can be rotated about the center axis of the support member by rotating the support member, and an injection nozzle disposed to inject a blast material against the work pieces from the outside of the tubular barrel rotated about the center axis.
According to a sixth aspect and feature of the present invention, in addition to the fifth feature, a plurality of the tubular barrels are supported in an annular shape circumferentially outside the center axis of the support member.
According to a seventh aspect and feature of the present invention, in addition to the fifth feature, the tubular barrel and/or the support member for supporting the tubular barrel is detachably mounted.
According to an eighth aspect and feature of the present invention, there is provided a process for blasting surfaces of work pieces using a blasting apparatus according to the first or fifth feature.
According to a ninth aspect and feature of the present invention, in addition to the eighth feature, the work pieces are rare earth metal-based permanent magnets.
According to a tenth aspect and feature of the present invention, there is provided a process for treating the surfaces of rare earth metal-based permanent magnets, comprising the steps of removing an oxide layer formed on the surface of each of the rare earth metal-based permanent magnets using a blasting apparatus according to the fourth or seventh feature, removing the tubular barrel containing the rare earth metal-based permanent magnets with the oxide layers removed therefrom, or the support member for supporting the tubular barrel from the blasting apparatus, and attaching the tubular barrel or the support member to a vapor deposited film forming apparatus, where a metal film is formed on the surface of each of the rare earth metal-based permanent magnets by a vapor deposition process.
According to an eleventh aspect and feature of the present invention, in addition to the tenth feature, the process further includes a step of removing the tubular barrel containing the rare earth metal-based permanent magnets having the metal films formed thereon, or the support member for supporting the tubular barrel from the vapor deposited film forming apparatus, and attaching the tubular barrel or the support member again to the blasting apparatus according to the fourth or seventh feature, where the metal films are subjected to a shot peening.
With the blasting apparatus according to the first feature of the present invention (a first embodiment of the present invention) in which the injection nozzle is disposed to inject the blast material against the work pieces from the outside of the tubular barrel formed of the mesh net for accommodation of the work pieces and rotatable about the center axis, the work pieces can be stirred homogenously and efficiently without excessive occurrence of the collision of the work pieces against one another and without occurrence of the collision of the work pieces against one another with a strong shock force. Therefore, the treating efficiency is enhanced and moreover, it is possible to inhibit the occurrence of the cracking and breaking of the work pieces. Since the tubular barrel is formed of the mesh net, the blast material can be injected from all directions. Therefore, any number of injection nozzles for injecting the blast material can be disposed at any locations in any manner, so that the blast material can be injected uniformly and efficiently against the work pieces.
With the blasting apparatus according to the fifth feature of the present invention (a second embodiment of the present invention) in which the tubular barrel formed of the mesh net for accommodation of the work pieces and supported circumferentially outside the center axis of the support member rotatable about the center axis, for rotation about the center axis, so that the tubular barrel can be rotated about the center axis of the support member by rotating the support member, and the injection nozzle is disposed to inject the blast material against the work pieces from the outside of the tubular barrel rotated about the center axis, it is possible to more inhibit the occurrence of the cracking and breaking of the work pieces, in addition to the effect provided in the blasting apparatus according to the first feature of the present invention.